Piloting the Plane of Nutrition During Turbulent Drought Conditions

by Macey Mueller for the Red Angus Genetic Advancement Edition

A cow’s prenatal nutrition influences everything from colostrum quality and milk yield to her calf’s immune system and her ability to breed back on time. Providing adequate nutrition is critically important during the third trimester and through the breeding season, and years of research shows negative energy balance (weight loss) prior to calving and during early lactation can result in reduced cow and calf performance.

This is perhaps most evident in spring-calving herds, where low-quality winter forage and tough weather conditions coincide with increasing nutritional demands – energy requirements increase by about 20% between the second and third trimester and then surge an additional 40% during the early stages of lactation.

Nutritional needs are further compounded when you factor in the current widespread drought conditions. Many cows grazed dehydrated summer forages that were likely in early dormancy and lacking in adequate vitamins and minerals. Furthermore, many winter diets this year include late-harvested hay, crop residue or failed crops. With little hay carryover from 2021 and drought conditions throughout much of 2022, producers had to be creative to find enough roughage to winter their cows.

David Lalman, Ph.D, Oklahoma State University extension beef cattle specialist, said current forage conditions across much of the country are concerning and require special attention to maintain spring cow condition through a demanding nutritional season.

Research shows mature cows calving in body condition score 5 or greater produce enough colostrum with adequate concentrations of immunoglobulins, which are important in creating a calf’s initial passive immunity. She should maintain that condition through early lactation to optimize her potential to breed back early.

“When cows calve in thin condition, postpartum interval (the time from calving to the first estrous cycle) is extended, and the further below BCS 5 those cows are at calving time, the longer the postpartum interval will be. The result is fewer cows cycling and breeding early when the bulls are turned out,” Lalman said. “Avoiding negative energy balance can be difficult and expensive in years like this with limited forage, especially in herds calving early. After calving, the goal should be to maintain cow body condition or to at least minimize her weight loss.”

Determining Supplementation Needs

Forage testing is fundamental to beef cattle nutrition and essential to best determine supplementation needs. Lalman said test fees typically range from $15 to $50, depending on the level of information desired. Test results can be combined with other pertinent information in a decision-making tool like OSU’s Cowculator to explore gaps or excesses in a nutritional plan and to evaluate various forage and supplement options.

Oklahoma State University’s David Lalman recommends using forage tests to identify supplementation needs, as a positive and consistent plane of nutrition is critical during a cow’s third trimester and through the breeding season.

Piloting the Plane of Nutrition During Turbulent Drought Conditions

“With a forage test and a little time working with a ration evaluation program, you should be able to determine whether that forage is adequate for protein, energy and mineral,” he said. “In most cases, there will be deficiencies or excesses, and you can use the program to determine how well different supplement options fill those gaps left by the forage base and how much of the supplement you should feed.”

Taking the time to calculate available nutrients can also be financially beneficial. When you consider that nutrition expenses – pasture, purchased and harvested hay, and concentrate feeds – make up between 40% and 50% of the annual cost to maintain a cow, it is easy to see how efficient supplementation can affect your bottom line.

For example, with a hay test, some producers are going to discover their hay contains inadequate protein to maintain a cow during gestation – about 8% of diet dry matter. However, some will discover their hay contains 9% protein or more. In those cases, especially during gestation, supplementation may not be required. That could lead to savings as much as $1 per head, per day.

A free-choice mineral program is a relatively easy and inexpensive solution to supplement vitamin deficiencies.

“Minimizing the cost of production is the key to being profitable in a commercial cow-calf operation,” he said. “A 2021 Kansas State University study shows that differences in production costs account for about two-thirds of the difference between the most profitable and the least profitable cow-calf operations. In comparison, differences in revenue due to production (i.e. weaning weight and price) accounted for about one-third of the difference between the most and least profitable operations.

OSU Cowculator

The OSU Cowculator is a Microsoft Excel spreadsheet designed to assist cattle producers in making informed decisions associated with beef cow nutrition. The user-friendly software program considers the type of animal, stage of production, breed, weight and forage test results and provides supplementation recommendations based on the body condition change or maintenance desired during the feeding period being evaluated.

For more information or to request access to the OSU Cowculator, visit extension.okstate.edu/programs/cowculator.html. //

Piloting the Plane of Nutrition During Turbulent Drought Conditions

“Reconciling nutritional needs with a hay test and a ration evaluation program is the first step in evaluating opportunities to cut back on winter nutrition costs.”

Avoid Vitamin A Deficiencies

In addition to reduced energy and protein levels in forages, drought years can also lead to vitamin A deficiencies, which can affect both cow and calf. Cattle have the ability to convert the carotene found in the green pigment of plants into the active form of vitamin A, and during a grazing season with average moisture levels, cows can usually consume enough vitamin A stores to last two to three months.

Unfortunately, Lalman said a lot of the forage grazed and harvested this past year had lost most of its green and subsequently, its carotene concentration.

“Regardless of the year, vitamin A generally declines rapidly in forage as it becomes more mature through the fall, and the carotene concentration of that forage drops down close to zero,” he explained. “As we saw this past year, that process can happen a lot earlier during a drought.”

While it is nearly impossible to see symptoms of vitamin A deficiencies in cows, Lalman said it can reduce a newborn calf’s ability to establish a strong immune system and cause late-term abortions, stillborn calves and retained placentas.

Fortunately, vitamin A supplementation is both relatively easy and inexpensive, and during the grazing season is typically achieved through a free-choice mineral program.

Lalman said a gestating cow requires about 30,000 international units of vitamin A per day, and that number increases to nearly 55,000 IU per day for a lactating cow.

Nutritional Consistency Matters

Lalman said it is becoming apparent that radical changes in a cow’s diet or nutritional plane around the time of breeding can cause detrimental early embryonic loss, with some data indicating a 10% decline in timed AI conception rates.

“A common scenario might be to maintain cows in a drylot or sacrifice pasture where hay and supplement is fed, then once timed AI is completed or bulls are turned in, the cows are turned out on lush green pasture,” he said.

“That represents a sudden change in their diet and plane of nutrition, and Dr. George Perry’s work has shown that those radical changes can result in lower early breeding success.

“Instead, just prior to and during the breeding season, diet changes should be gradual if possible. This may require adjustments in the timing of breeding (calving season) as well as the nutritional program.” //

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